Ceramic article



Nov. 12, 1935o w.` J. scoTT Er Al. 2,020,477

CERAMIC ARTICLE Filed oct. 2v, 193s /A/ VE' N 70H5 W; J. Sca 77' 5. R. MAso/v 5y fm.

Patented t Nov. 1.27,' 1935` PATENT; Ao-l-#Flci-r.

CERABIIC ARTICLE Walter J. Scott, Brookiield, and Sumner R. Mason, Wilmette, Ill., assignors to Western Electric Company, Incorporated poration of New York New York, N. Y., a cor- Applicatlon October 27, 1 933, Serial No. 695,420 7 Claims.' (Cl. 91-73) f Thisinvention relates to ceramic articles and A good coverage may Vbe obtained with a single enamel coating.

,115 A complete understanding of the invention may be had by reference to the following description taken in conjunction with the accompanying drawing, in which Fig. 1 is a plan view of a telephone number plate embodying the invention; and

Fig. 2 is an enlarged sectional view taken onlin 2-2 of Fig. 1. In applying an enamel coating to ceramic articles, such as number plates for telephone dials. it 25 is frequently convenient t0 apply the enamel coating only upon the face of the plates because when the entire platev is coated with enamel, diiliculty is often experienced in meeting the close dimensional requirements for seating the plates 30 "in the dials. The'covering of only the face of the number plate with an enamel coating entails the necessity of protecting the remainder of the number plate against corrosion.

In producing a number plate, a circular plate 5 35 of iron, steel, or other suitable material is made and grooves 1 are provided along the inner and outer peripheral-edges of the plate. One side of the grooves is made substantially vertical and the other side relatively flat, thus leaving ridges 8 40 along the edges.

rounded, as shown in Fig. 2, so that' when the ceramic materialsare dusted on the plate they will collect in an even layer on the plate, except for the ridges, from which the material` will fall 45 off on account of the curved or arcuate faces of the ridges. The ,plate is then red to fuse the ceramic materials to form the enamel coating. A

sharp outline of the enamel will be formed along the edges and the ridge will protect the edge of 50 the enamel to prevent edge cracking of the enamel.

The provision of a ridge adjacent to the edge.

g of the article forms no part of the present invention and is described and claimed in the copend- A ing application of W. J. Scott, Serial No. 657,251, 55 filed February 17, 1933.

The ridges 8 are preferably.

Whenonly the face of the number plate is covered with enamel, it is necessary to protect the rest of the plate against corrosion. This may be accomplished by providing the entire plate with a protective black iron oxide coating by a process 5 sometimes known as Bower-Baring. The application of the black iron oxide coating is more fully described in. the copending application of W. J. Scott for ceramic articles, now Patent No. 1,962,751, issued June 12, 1934. An anernative 10 method of protecting the'portion of the number plate which is not enameled is to copper plate the number plate and then apply a nickel plating over the copper plate. 'I'he ceramic materials may then be dusted on the face of the plate and fused to form an enamel coating. It has been found that when it is attempted to use only a copper plating over the iron base, the copper tends to oxidize and burn olf during the fusing of the enamel. If a nickel coating is used alone under the enamel coating, it appears that the nickel reacts with the iron to form gases which cause a blistering of the enamel coating. By first copper plating the number plate and then nickel plating over the copper plate, these diculties are avoided and a firm adherent enamel coating may then be applied to the nickel coating. The copper and nickel coatings may be applied by any well known method, preferably by electroplating. The nickel coating over the copper coating provides a highly protective covering against corrosion of that portion of the surface of the number plate which is not covered by enamel.

While the best results are obtained by placing the copper coating under the nickel coating, good results are also obtained by placing the nickel coating under the copper coating. In practice about 25 milligrams of copper per square inch are plated on the base over which is plated about 30 milligrams per square inch of nickel. 40

The enamel coating may be applied as a single coating or in some cases it may be desirable to apply several coatings. When several coatings are applied tothe number plate, a tacky subl stance, such as ceramic ink varnish, may or may not be applied between the successive layers of enamel. After the enamel coating is applied, the l character, background, or ornamental markings are applied. It has been found that when a single coating of enamel is used, it is desirable to use an opacier in the ink varnish for the markings. Suitable opaciers that may be used are tin oxide, arsenic oxide, or cryolite.

After the enameling material has been dusted on the number plate, the enamel is iired at a perienced during this firing operation. However,

during the later firing of the article to fuse the character, background, or ornamental ceramic markings into the enamel, the temperature may 4 not be raised to the nring temperature above mentioned and under these conditions the enamel has a tendency to blister. After' the enamel has -been formed on the number plate, the enamel is provided with characr markings. In some cases a background color is applied to the enamel and characters consisting of numbers and letters are applied to the enamel. -The background color is formed by applying a colored' enameling material or a ceramic ink to the enamel surface. After the background color has been applied, the plate is placed in an oven and baked at a temperature of about 300 F. to harden the colored enamel so that it will not become marre'd in subsequent printing operations. The letters of the number plate are usually in black and are printed on the number plate with a ceramic ink. 'I'he plate is then again baked at a temperature of about 300 F. The letters of the number plaie are usually colored red and are applied by printing the letters with a ceramic ink of a Ireci color. After the red characters'have been applied, thel entire plate is again fired. This tiring temperature for fusing the characters and background onto the enamel is carried out at a lower temperature than the firing of the original enamel coating, since otherwise the characters tend to run or spread on the enamel. It has been found that by firing the plates for the background and character fusing operations at a uniform low temperature, there is a tendency for blisters to form in the enamel coating. This tendency has been overcome by ilring the number of plates at an initial temperature of 1160 F. and increasing the temperature to a final temperature of approximately 1310l F. during a period of about 4.4

yminutes.

While the invention has been described in con- ,nection with the manufacture o! number plates i'oz telephone dials, it will be understood that the invention is equally applicable to enameling other types of articles and providing character markings thereon. It will be understood, therefore. that the nature and embodiment of the invention described herein is merely illustrative and that 5 many changes and modifications may be matiev therein without departing from the scope and spirit of the invention.

What is claimed is:

1. A method of forming a ceramic article which l comprises copper plating a ferrous metal base. nickel plating thereover, and applying an enamel coating over the nickel plate.

2. A ceramic article comprising a ferrous metal base, a copper coating thereon, a nickel coating l on the copper coating, and an enamel coating over the nickel coating.

3. A ceramic article comprising an iron base,

a copper plated coating thereover, a nickel plated coating over the copper plated coating, and an enamel coating over the nickel plated coating.

4. A ceramic article comprising a ferrous metal base, copper and nickel coatings on said base, andv an enamel. coating over said coatings.

5. A method of forming a ceramic article which comprises successively applying a copper and nickel coating on a ferrous metal base, applying ceramic material to the coated base, and iiring the article to fuse the material and form an enameled coating.

6. A method of forming a ceramic article which comprises successively applying a copper and a nickel coating tov an iron base, applying ceramicr material to the base, and ring the article at a temperature of the order of 1575 F. to fuse the material and form an adherent coating.

7. A method of forming a ceramic article which comprises successively applying a copper and a nickel coating to an iron base, applying ceramic material to the base, firing the article at a tem- 40 

